Octalink Non-Drive Side Crank Arm Continually Loosens

I've got an Octalink crankset, and the non-drive side crank arm continually loosens up. Even on shorter rides, in the middle of the ride, it will become loose. I am going to try loc-tite, but not sure that will even work, and it is tiresome having to bring an 8mm allen, and continually stop to tighten it up.

Is this a common trait, and is there a cure, or should I just junk the whole system, and get a new crankset and bottom bracket.

if you aren't using a torque wrench you're probably not tightening the fastener nearly enough. if memory serves, the nominal value is 38 ft/lb. hopefully you haven't hogged out the splined interface through the repeated loosening. tightened correctly an octalink interface will not be coming loose.

Before resorting to loctite, follow corsa's suggestion. I believe it's 36 ft-lbs, but what a couple between friends? (Acutally, I just round down to 35).

Loctite may help if the bolt is properly torqued and still working loose, but it will almost certainly not work if the bolt isn't properly tightened in the first place.

Three Octalink cranksets, on three different bikes, beginning with an LX set circa '99, and proper torque is all I've ever needed. Remember, if you don't have a torque wrench, 35 ft-lbs equates to about 70 pounds of force on the tip of a 6" allen wrench. That's more than snug!

This issue is not uncommon with Octalink, and is the only real problem with it. Typically it develops when the crank is allowed to come loose once, and gets ridden that way for a while. It classically develops a creak when this happens. The spline on the crank gets wallowed (a bit), and from then on, it comes loose as you ride it. Because it is caused by damage to the spline, it sometimes is not fixable.

Try removing both crank arms, rotating the BB spline to another position, and re-installing. Make sure the bolt is tight, Octalink has a bottom out stop, so you cannot over tighten the crank bolt like square taper (unless you strip the bolt, which is bad! But that's pretty hard to do). If it's still coming loose, it can't hurt to try some locktite on the threads.